12 research outputs found
Energy-twisted boundary condition and response in one-dimensional quantum many-body systems
Thermal transport in condensed matter systems is traditionally formulated as
a response to a background gravitational field. In this work, we seek a
twisted-boundary-condition formalism for thermal transport in analogy to the
twisted boundary condition for electrical transport. Specifically, using
the transfer matrix formalism, we introduce what we call the energy-twisted
boundary condition, and study the response of the system to the boundary
condition. As specific examples, we obtain the thermal Meissner stiffness of
(1+1)-dimensional CFT, the Ising model, and disordered fermion models. We also
identify the boost deformation of integrable systems as a bulk counterpart of
the energy-twisted boundary condition. We show that the boost deformation of
the free fermion chain can be solved explicitly by solving the inviscid Burgers
equation. We also discuss the boost deformation of the XXZ model, and its
nonlinear thermal Drude weights, by studying the boost-deformed Bethe ansatz
equations
Non-Hermitian boost deformation
The Hatano-Nelson model is one of the most prototypical non-Hermitian models
that exhibit the intrinsic non-Hermitian topological phases and the concomitant
skin effect. These unique non-Hermitian topological phenomena originate from
the Galilean transformation. Here, we extend such an idea to a broader range of
systems based on an imaginary boost deformation and identify the corresponding
energy-twisted boundary conditions. This imaginary boost deformation
complexifies spectral parameters of integrable models and can be implemented by
the coordinate Bethe ansatz. We apply the imaginary boost deformation to
several typical integrable models, including free fermions, the
Calogero-Sutherland model, and the XXZ model. We find the complex-spectral
winding in free fermion models in the periodic boundary conditions and the
non-Hermitian skin effect in the open boundary conditions. The interaction
effect is also shown in the two-particle spectrum of the XXZ model.Comment: 13 pages, 8 figure
Spatial deformation of many-body quantum chaotic systems and quantum information scrambling
We study the effect of spatial inhomogeneity on quantum information
scrambling, a process of spreading and locally hiding quantum information in
quantum many-body systems. As a paradigmatic example, we consider the quantum
chaotic Ising spin chain and its inhomogeneous counterpart that is obtained by
modulating the Hamiltonian density. Specifically, we consider the so-called
M\"obius and sine-square deformations that were previously studied in the
context of (1+1)-dimensional conformal field theories ( d CFTs). In the
spatial region where the modulated energy density is small, these deformations
prevent the spreading of quantum information while in the region where the
modulated energy density is large quantum information scrambling is
accelerated. This suggests that we can control the scrambling and butterfly
effect by spatially modulating the Hamiltonian density. We also found that the
time dependence of energy density exhibits the signature of black-hole-like
excitation found in the d CFTs even in the chaotic spin chain.Comment: 16 pages, 11 figure
Why Virtue Ethics?
Contemporary virtue ethics, an agent-centred ethical theory, has been presented as a response to inadequacies in more traditional act-centred theories. In this paper, I argue that such a response is insufοcient: contemporary virtue ethics fails to avoid the inadequacies that it purports to avoid, and brings with it problems of its own. This paper is divided into 5 sections, in the οrst of which I introduce contemporary virtue ethics as an agent-centred and pluralistic ethical theory. In section 2, I present inadequacies that virtue ethics claims to avoid: being too reductive, too algorithmic, too abstract, self-effacing, and self-other asymmetric. In section 3, I consider and analyse virtue ethics’ account of right action and of motives in order to argue in section 4 that, if these inadequacies are indeed problems affecting traditional ethical theories, virtue ethics does not avoid these problems either— particularly because of its basis in the concept of virtues and its heavy reliance on phronesis. I show that another ethical theory, limited moral pluralism, has the same advantages of not being overly reductive, algorithmic, or abstract, and being self-other symmetric, and that virtue ethics does not avoid self-effacement as it claims to. I also question here whether self-effacement and self-other asymmetry should be considered problems when evaluating moral theories. Finally, I suggest in section 5 that virtue ethics is open to further criticisms of indeterminacy and lack of explanatory power
Epitaxial growth, magnetoresistance, and electronic band structure of GdSb magnetic semimetal films
Motivated by observations of extreme magnetoresistance (XMR) in bulk crystals
of rare-earth monopnictide (RE-V) compounds and emerging applications in novel
spintronic and plasmonic devices based on thin-film semimetals, we have
investigated the electronic band structure and transport behavior of epitaxial
GdSb thin films grown on III-V semiconductor surfaces. The Gd3+ ion in GdSb has
a high spin S=7/2 and no orbital angular momentum, serving as a model system
for studying the effects of antiferromagnetic order and strong exchange
coupling on the resulting Fermi surface and magnetotransport properties of
RE-Vs. We present a surface and structural characterization study mapping the
optimal synthesis window of thin epitaxial GdSb films grown on III-V
lattice-matched buffer layers via molecular beam epitaxy. To determine the
factors limiting XMR in RE-V thin films and provide a benchmark for band
structure predictions of topological phases of RE-Vs, the electronic band
structure of GdSb thin films is studied, comparing carrier densities extracted
from magnetotransport, angle-resolved photoemission spectroscopy (ARPES), and
density functional theory (DFT) calculations. ARPES shows hole-carrier rich
topologically-trivial semi-metallic band structure close to complete
electron-hole compensation, with quantum confinement effects in the thin films
observed through the presence of quantum well states. DFT predicted Fermi
wavevectors are in excellent agreement with values obtained from quantum
oscillations observed in magnetic field-dependent resistivity measurements. An
electron-rich Hall coefficient is measured despite the higher hole carrier
density, attributed to the higher electron Hall mobility. The carrier
mobilities are limited by surface and interface scattering, resulting in lower
magnetoresistance than that measured for bulk crystals
Revealing quantum Hall states in epitaxial topological half-Heusler semimetal
Prediction of topological surface states (TSS) in half-Heusler compounds
raises exciting possibilities to realize exotic electronic states and novel
devices by exploiting their multifunctional nature. However, an important
prerequisite is identification of macroscopic physical observables of the TSS,
which has been difficult in these semi-metallic systems due to prohibitively
large number of bulk carriers. Here, we introduce compensation alloying in
epitaxial thin films as an effective route to tune the chemical potential and
simultaneously reduce the bulk carrier concentration by more than two orders of
magnitude compared to the parent compound. Linear magnetoresistance is shown to
appear as a precursor phase that transmutes into a TSS induced quantum Hall
phase on further reduction of the coupling between the surface states and the
bulk carriers. Our approach paves the way to reveal and manipulate exotic
properties of topological phases in Heusler compounds.Comment: 8 pages, 4 figures. Supplementary Infromation contains 7 sections and
17 figure
New growth rises out of historic ruin: Adaptive reuse of Christchurch Cathedral
RESEARCH QUESTION:
How could the Christchurch Cathedral be rebuilt and adapted using contemporary technology to meet the demands of a modern society and economy?
ABSTRACT:
In New Zealand, in 2011, Christchurch Cathedral was severely damaged in an earthquake. Before the 2011 earthquake, the Cathedral and Cathedral Square were the physical and social centre of Christchurch. For locals and tourists, Cathedral Square is not just a religious place, but also a centre of leisure and entertainment. But, for almost a decade after 2011, the site has been closed due to safety issues. Initially, Bishop Victoria Matthews decided the original Cathedral should be demolished and replaced with a new, contemporary design. But various groups opposed the intention of the church and, through negotiations, the Anglican Church finally decided in 2017 to reinstate the Cathedral using a combination of repair, restoration, reconstruction/rebuild and seismic strengthening. However, to restore the Cathedral to its original appearance using traditional technologies and materials is also a kind of damage to the history and memory of the Cathedral, because too much restoration work makes the line between the new and the old difficult to identify. And if the Cathedral is fully reconstructed or restored to its original form, will the history or the memory associated with the time of earthquake be ignored or reduced
Exploring the Diverse Expectations of Stakeholders in Industrial Land Redevelopment Projects in China: The Case of Shanghai
Use of Continuous-Flow Microextraction and Liquid Chromatography for Determination of Phoxim in Water Samples
Transiting Exoplanet Monitoring Project (TEMP). III. On the Relocation of the Kepler-9 b Transit
The Kepler-9 system harbors three known transiting planets. The system holds significant interest for several reasons. First, the outer two planets exhibit a period ratio that is close to a 2:1 orbital commensurability, with attendant dynamical consequences. Second, both planets lie in the planetary mass “desert” that is generally associated with the rapid gas agglomeration phase of the core accretion process. Third, there exist attractive prospects for accurately measuring both the sky-projected stellar spin-orbit angles as well as the mutual orbital inclination between the planets in the system. Following the original Kepler detection announcement in 2010, the initially reported orbital ephemerides for Kepler-9 b and c have degraded significantly, due to the limited time base-line of observations on which the discovery of the system rested. Here, we report new ground-based photometric observations and extensive dynamical modeling of the system. These efforts allow us to photometrically recover the transit of Kepler-9 b and thereby greatly improve the predictions for upcoming transit mid-times. Accurate ephemerides of this system are important in order to confidently schedule follow-up observations of this system, for both in-transit Doppler measurements as well as for atmospheric transmission spectra taken during transit